Novel chiral di-2-pyridyl ketone ligands: Crystal structure of a copper complex and its activity in the copper-catalyzed enantioselective cyclopropanation of styrene

New Ct-symmetric chiral di-2-pyridyl ketones were prepared from readily ava ilable chiral bromopyridines. Their complexes with copper were synthesized and characterized by X-ray crystallography. The copper complexes were prepa red in situ with the triflate anion and were found to be active in the cata lysis of cyclopropanation with diazo esters and alkenes. Reaction yields we re excellent and enantioselectivities of up to 61% were observed.